The present invention relates to semiconductor manufacturing methods, plasma processing methods and plasma processing apparatuses for increasing the yield of material to be processed such as a semiconductor substrate by in-situ (on-the-spot) measuring sub-micron foreign particles floating in the course of processing in a plasma processing chamber without being affected external disturbances such as plasma emitted light.
Prior arts for monitoring foreign particles floating in a plasma processing chamber are disclosed in several documents. In the following description, prior arts disclosed in Japanese Patent Laid-open Nos. Sho 57-118630, Hei 3-25355, Hei 3-147317, Hei 6-82358 and Hei 6-124902 are referred to as prior arts 1 to 5 respectively.
Prior art 1 cited above introduces a depositing apparatus which comprises a means for radiating parallel lights in a reaction space wherein the parallel lights have a spectrum different from the spectrum of a light self emitted in the reaction space and a means for detecting lights scattered from infinitesimal particles generated in the reaction space due to radiation of the parallel lights.
Prior art 2 cited above introduces an infinitesimal-particle measuring apparatus for measuring floating infinitesimal particles and infinitesimal particles stuck to the surface of a semiconductor substrate for making semiconductor devices by using a scattering phenomenon of laser beams. The infinitesimal-particle measuring apparatus comprises: a laser-beam-phase modulating unit for generating 2 laser beams having equal wavelengths and a difference in phase modulated at a predetermined frequency; an optical system for directing the 2 laser beams to intersect each other in a space containing infinitesimal particles being measured; a light detecting unit for receiving lights scattered by the infinitesimal particles being measured in an area where the 2 laser beams intersect each other and converting the received lights into an electrical signal; and a signal processing unit for extracting a signal component having a frequency equal to the frequency of a phase modulation signal used in the laser-beam-phase modulating unit or a frequency twice the frequency of the phase modulation signal and a difference in phase from the phase modulation signal unchanged with the lapse of time out off the electrical signal representing the scattered lights.
Prior art 3 cited above is a technology for measuring the degree of pollution in a reactor by analyzing scattered lights. The art includes the steps of: a scanning operation by using a radiated coherent light to generate lights scattered in the reactor on the spot; and detecting the lights scattered in the reactor.
Prior art 4 cited above introduces a particle detecting apparatus which comprises: a laser means for generating a laser beam; a scanner means for scanning an area in a reactor chamber of a plasma processing tool including particles to be measured by using the laser beam; a video camera means for generating a video signal representing laser beams scattered by particles in the area; and a means for processing the video signal and displaying an image of the video signal.
Prior art 5 cited above introduces a plasma processing apparatus which comprises: a camera apparatus for observing a plasma generation area in a plasma processing chamber; a data processing unit for obtaining desired information by processing a picture taken by the camera apparatus; an exhaust means for reducing the number of particles by using the information produced by the data processing apparatus; and a control unit for controlling at least one of a process-gas introducing means, a high-frequency-voltage applying means and a purge-gas introducing means.
Referred to as prior art 6, an infinitesimal-particle measuring apparatus used in control of advanced cleaning processes such as semiconductor manufacturing processes and chemical manufacturing processes is disclosed in Japanese Patent Laid-open No. Sho 63-71633. Used for detecting scattered lights from particles in a liquid sample due to radiation of a laser beam to an infinitesimal area of a container flowing the liquid sample being examined, the infinitesimal-particle measuring apparatus provided by prior art 6 comprises: a means for carrying out intensity modulation on the laser beam at a fixed frequency; and a phase detector for measuring a signal coming from a detector having a frequency equal to the frequency of the intensity modulation.
In the plasma processing apparatus, a substance generated by a reaction occurring in a plasma process is deposited on the surface wall of the plasma processing chamber or an electrode. With the lapse of time, however, such a substance is peeled off, becoming a floating infinitesimal foreign particle. The floating infinitesimal foreign particle is stuck to a material to be processed in the course of plasma processing, resulting in a bad product. In other cases, the floating infinitesimal foreign particle is trapped on a bulk-sheath boundary surface and falls on the material to be processed at the time a plasma discharging phenomenon is terminated at the end of the plasma processing. The foreign particle stuck to the material to be processed gives rise to a poor characteristic and an appearance defect. As a result, such a substance decreases the yield of materials to be processed such as semiconductor substrates.
In the mean time, the degree of integration of circuit patterns created on a material to be processed such as a semiconductor substrate has been becoming higher and higher. In the semiconductor field, for example, the integration of circuit patterns in the DRAM is under way, increasing the capacity of the DRAM to 256 Mbit and even to 1 Gbit. That is to say, the minimum line width of the circuit patterns is in a process of being miniaturized to a size in the range 0.25 to 0.18 xcexcm. It thus becomes necessary to also measure infinitesimal foreign particles on the order of down to sub-microns which float in the plasma or in an area in proximity to the plasma.
Thus, required in the plasma processing apparatus is a capability of measuring also the infinitesimal foreign particles of the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma without being affected by an external disturbance such as plasma emitted light. Since the plasma emitted light exhibits a continuous wavelength spectrum over a range from a zone beyond the ultraviolet ray to a zone beyond the near-infrared ray, however, it is difficult to separate infinitesimal foreign particles of the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma from the plasma emitted light in order to detect the foreign particles by using the spectrum generated in accordance with prior art 1.
As described above, in either of prior arts 1 to 5, there is no consideration of a matter regarding an attempt to separate very weak scattered lights generated by infinitesimal foreign particles on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma from the plasma emitted light in order to detect the scattered lights.
In addition, in prior art 6 used for measuring the number of particles in a liquid sample flowing to a container, there is also no consideration of a matter regarding an attempt to separate very weak scattered lights generated by infinitesimal foreign particles of the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma from the plasma emitted light in order to detect only the scattered lights.
It is thus an object of the present invention addressing the problems described above to provide a plasma processing method and a plasma processing apparatus for improving the yield of materials to be processed by enabling real-time monitoring of a state of pollution in a plasma processing chamber through substantial enhancement of the detection sensitivity to detect infinitesimal foreign particles on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma in the course of plasma processing in the plasma processing chamber by separating the light scattered by the foreign particles from a plasma emitted light.
It is another object of the present invention to provide a semiconductor manufacturing method which allows a semiconductor device with a high quality to be manufactured at a high yield by enabling real-time monitoring of a state of pollution in a plasma processing chamber through substantial enhancement of the detection sensitivity to detect infinitesimal foreign particles on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma in the plasma processing chamber by separating the light scattered by the foreign particle from a plasma emitted light.
By the way, in order to achieve the objects described above, the present invention provides a semiconductor manufacturing method for manufacturing a semiconductor by generating a plasma in a processing chamber and carrying out processing on a semiconductor substrate by using the plasma, comprising the steps of:
preparing a floating-foreign-particle measuring apparatus including a light radiating optical system for radiating a light having a desired wavelength and completing intensity modulation at a desired frequency to the processing chamber; a scattered-light detecting optical system for separating a component with the desired wavelength from scattered lights obtained from the processing chamber as a result of radiation of the light by the light radiating optical system, for optically receiving the component and for converting the component into a first signal; and a foreign-particle-signal extracting unit (means) which separates a second signal representing foreign particle floating in the plasma or in an area in proximity to the plasma from a third signal obtained by emission of the plasma for detection of the second signal by extraction of a component with the desired frequency used for the intensity modulation from the first electrical signal obtained from the scattered-light detecting optical system; and
measuring foreign particle floating in the plasma or the area on base of said second electrical signal being detected from said foreign-particle-signal extracting unit by using the floating-foreign-particle measuring apparatus.
In addition, the present invention also provides a plasma processing method for generating a plasma in a processing chamber and carrying out processing on material to be processed by using the plasma, comprising the steps of:
preparing a floating-foreign-particle measuring apparatus including a light radiating optical system for radiating a light having a desired wavelength and completing intensity modulation at a desired frequency to the processing chamber; a scattered-light detecting optical system for separating a component with the desired wavelength from scattered lights obtained from the processing chamber as a result of radiation of the light by the light radiating optical system, for optically receiving the component and for converting the component into a first signal; and a foreign-particle-signal extracting unit (means) which separates a second signal representing foreign particle floating in the plasma or in an area in proximity to the plasma from a third signal obtained by emission of the plasma for detection of the second signal by extraction of a component with the desired frequency used for the intensity modulation from the first signal obtained from the scattered-light detecting optical system; and
measuring foreign particle floating in the plasma or the area on base of said second signal being detected from said foreign-particle-signal extracting unit by using the floating-foreign-particle measuring apparatus.
Furthermore, the present invention also provides a plasma processing apparatus for generating a plasma in a processing chamber and carrying out processing on material to be processed by using the plasma, comprising a floating-foreign-particle measuring apparatus including:
a light radiating optical system for radiating a light having a desired wavelength and completing intensity modulation at a desired frequency to the processing chamber;
a scattered-light detecting optical system for separating a component with the desired wavelength from scattered lights obtained from the processing chamber as a result of radiation of the light by the light radiating optical system, for optically receiving the component and for converting the component into a signal; and
a foreign-particle-signal extracting unit (means) for separating a signal representing foreign particle floating in the plasma or in an area in proximity to the plasma from that emitted by the plasma for detection of the signal representing the foreign particle by extraction of a component with the desired frequency used by the intensity modulation from the signal obtained from the scattered-light detecting optical system.
Moreover, the present invention also provides a plasma processing apparatus for generating a plasma in a processing chamber and carrying out processing on material to be processed by using the plasma, comprising a floating-foreign-particle measuring apparatus including:
a light radiating optical system for radiating a light having a desired wavelength and completing intensity modulation at a desired frequency to the processing chamber;
a back-scattered light detecting optical system for separating a component with the desired wavelength from back-scattered lights obtained from the processing chamber as a result of radiation of the light by the light radiating optical system, for optically receiving the component and for converting the component into a first signal; and
a foreign-particle-signal extracting unit (means) which separates a second signal representing foreign particle floating in the plasma or in an area in proximity to the plasma from a third signal obtained by emission of the plasma for detection of the second signal by extraction of a component with the desired frequency used for the intensity modulation from the first signal obtained from the back-scattered light detecting optical system.
In the light radiating optical system provided by the present invention, an excitation frequency or an emission frequency of the plasma varies to a certain degree. Taking such variations into consideration, the frequency used in the intensity modulation is set at a value which deviates from the excitation or emission frequency of the plasma and a high-order harmonic frequency of the excitation or emission frequency by at least a difference in the range 10 to 15%.
Moreover, according to the present invention, an ion acceleration frequency and the frequency of a radio-frequency power supply for generating a voltage applied to a electrode on which a material to be processed is set are also included in the excitation or emission frequency of the plasma.
In addition, in the light radiating optical system provided by the present invention, a signal used in the intensity modulation has a rectangular waveform with a duty in the range 40 to 60%.
Furthermore, the back-scattered light detecting optical system provided by the present invention has a light shielding optical element for shielding a specular reflection light coming from the processing chamber.
Moreover, the light radiating optical system provided by the present invention has a scanning system for scanning the light across a surface of the material to be processed.
Moreover, the intensity-modulation frequency used in the light radiating optical system provided by the present invention is between the excitation or emission frequency of the plasma and a frequency of a direct-current component.
In addition, according to the present invention, there are provided:
an observation window provided on the processing chamber and used for transmitting the light radiated by the light radiating optical system and the scattered lights obtained from the processing chamber; and
a generated-substance-deposition preventing unit (means) provided in the processing chamber and used for preventing a generated substance from being deposited on an inner surface of the observation window.
Furthermore, the light radiating optical system employed in the plasma processing apparatus provided by the present invention has an optical system for converting a beam radiated to the processing chamber into a diffractionless beam or a Bessel beam.
Moreover, the light radiating optical system provided by the present invention has a configuration in which the diffractionless beam or the Bessel beam is formed only in a surface direction of a surface of the material to be processed so as to allow foreign particle floating in an area on a plasma bulk-sheath boundary surface to be detected.
Moreover, the light radiating optical system provided by the present invention has a configuration in which the diffractionless beam is generated by an axicon or an annular aperture optical system.
In addition, the light radiating optical system provided by the present invention has a configuration for radiating linear-polarization illumination light.
Furthermore, the back-scattered light detecting optical system employed in the plasma processing apparatus provided by the present invention has a polarization optical system for detecting backward-direction scattered lights coming from foreign particle floating in a plasma or in an area in proximity to the plasma.
Moreover, the present invention provides a semiconductor manufacturing method comprising:
a film-formation step of measuring foreign particle floating in a first plasma generated in a first processing chamber or a first area in proximity to the first plasma, while generating the first plasma in the first processing chamber and forming a film on a semiconductor substrate by using the first plasma, by using a first floating-foreign-particle measuring apparatus including: a first light radiating optical system for radiating a light having a desired wavelength and completing intensity modulation at a desired frequency to the first processing chamber; a first scattered-light detecting optical system for separating a component with the desired wavelength from scattered lights obtained from the first processing chamber as a result of radiation of the light by the first light radiating optical system, for optically receiving the component and for converting the component into a first signal; and a first foreign-particle-signal extracting unit (means) which separates a second signal representing foreign particle floating in the first plasma or in the area from a third signal obtained by emission of the first plasma for detection of the second signal by extraction of a component with the desired frequency used for the intensity modulation from the first signal obtained from the first scattered-light detecting optical system; and
an etching step of measuring foreign particle floating in a second plasma generated in a second processing chamber or foreign particle floating in a second area in proximity to the second plasma, while generating the second plasma in the second processing chamber and carrying out an etching process on a semiconductor substrate subjected to film formation by using the second plasma, by using a second floating-foreign-particle measuring apparatus including: a second light radiating optical system for radiating a light having a desired wavelength and completing intensity modulation at a desired frequency to the second processing chamber; a second scattered-light detecting optical system for separating a component with the desired wavelength from scattered lights obtained from the second processing chamber as a result of radiation of the light by the second light radiating optical system, for optically receiving the component and for converting the component into a forth signal; and a second foreign-particle-signal extracting unit (means) which separates a fifth signal representing foreign particle floating in the second plasma or in the area from a sixth signal obtained by emission of the second plasma for detection of the fifth signal by extraction of a component with the desired frequency used by the intensity modulation from the forth signal obtained from the second scattered-light detecting optical system.
As described above, the semiconductor manufacturing method provided by the present invention includes a film-formation process and an etching process.
According to the configurations described above, the detection sensitivity to detect infinitesimal foreign particle on the order of down to sub-microns floating in a plasma or in an area in proximity to the plasma can be increased substantially by separation of weak scattered lights generated by the infinitesimal foreign particle from a plasma emitted light for a detection purpose. As a result, it is possible to carry out real-time monitoring of a state of pollution in a plasma processing chamber and to reduce the number of inadvertently produced bad products due to foreign particle stuck thereto, allowing semiconductor devices with a high quality to be manufactured at a high yield.
In addition, according to the configurations described above, by using a diffractionless beam, uniform radiation of energy and detection at a uniform sensitivity can be implemented over the entire surface of a material to be processed. Moreover, by separating weak scattered lights generated by infinitesimal foreign particle on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma from a plasma emitted light for a detection purpose, the infinitesimal foreign particle on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma can be detected with a high degree of stability and at a substantially increased detection sensitivity over the entire surface of a material to be processed. As a result, it is possible to carry out real-time monitoring of the state of pollution in the plasma processing chamber.
Furthermore, according to the configurations described above, by separation of weak back-scattered lights generated from the infinitesimal foreign particle on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma from a plasma emitted light for a detection purpose, an observation window can be prevented against dirt with ease, a laser radiating optical system as well as a scattered-light detecting optical system can be made compact and the detection sensitivity to detect infinitesimal foreign particles on the order of down to sub-microns floating in the plasma or in an area in proximity to the plasma can be increased substantially. As a result, it is possible to carry out real-time monitoring of a state of pollution in a plasma processing chamber.